(1) Field of the Invention
The present invention is directed to a high-power high-isolation switch in which multiple high-power radio frequency (RF) sources which are phase controlled can switch power to one of several alternative output ports, in which the phase-control cannot maintain sufficient isolation of these ports. In addition, protection against burn-out during extraordinary leakage conditions is provided.
(2) Description of the Related Art
In the prior art, diode and gas tube switches are employed in radar systems to allow pulse RF power to be switched to one of a multiplicity of outputs. The diode and gas tube switches, however, are limited by their breakdown voltage and cannot handle high RF power while in a non-conductive state. Ferrite switches can be employed since they have a higher power capability, but generally they are limited to RF frequencies above 2.5 GHz.
In some applications, neither diode nor ferrite switches are feasible. In these cases, the RF power source is usually divided into N sub-units (N being an integer) whose outputs are combined in a matrix of hybrids or similar devices. If the RF amplitudes of the sub-units are maintained to be precisely equal and their output phase relationships are accurately controlled, their power can be made to add in one of the N outputs and cancel in the others. Phase can also be controlled in low power stages of the sub-units by using diodes. However, perfect cancellation in the undesired outputs is not achievable because of inaccuracy in phase and amplitude control. A 20 dB leakage is a typical leakage factor.
The present invention has been developed to overcome the above-mentioned problems of prior art devices.